1 /**
2 * JDBM LICENSE v1.00
3 *
4 * Redistribution and use of this software and associated documentation
5 * ("Software"), with or without modification, are permitted provided
6 * that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain copyright
9 * statements and notices. Redistributions must also contain a
10 * copy of this document.
11 *
12 * 2. Redistributions in binary form must reproduce the
13 * above copyright notice, this list of conditions and the
14 * following disclaimer in the documentation and/or other
15 * materials provided with the distribution.
16 *
17 * 3. The name "JDBM" must not be used to endorse or promote
18 * products derived from this Software without prior written
19 * permission of Cees de Groot. For written permission,
20 * please contact cg@cdegroot.com.
21 *
22 * 4. Products derived from this Software may not be called "JDBM"
23 * nor may "JDBM" appear in their names without prior written
24 * permission of Cees de Groot.
25 *
26 * 5. Due credit should be given to the JDBM Project
27 * (http://jdbm.sourceforge.net/).
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
30 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
31 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
32 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
33 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
34 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
35 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
36 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
38 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
39 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
40 * OF THE POSSIBILITY OF SUCH DAMAGE.
41 *
42 * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
43 * Contributions are Copyright (C) 2000 by their associated contributors.
44 *
45 * $Id: FreeLogicalRowIdPageManager.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $
46 */
47
48 package jdbm.recman;
49
50 import java.io.IOException;
51
52 /**
53 * This class manages free Logical rowid pages and provides methods
54 * to free and allocate Logical rowids on a high level.
55 */
56 final class FreeLogicalRowIdPageManager {
57 // our record file
58 private RecordFile file;
59 // our page manager
60 private PageManager pageman;
61
62 /**
63 * Creates a new instance using the indicated record file and
64 * page manager.
65 */
66 FreeLogicalRowIdPageManager(RecordFile file,
67 PageManager pageman) throws IOException {
68 this.file = file;
69 this.pageman = pageman;
70 }
71
72 /**
73 * Returns a free Logical rowid, or
74 * null if nothing was found.
75 */
76 Location get() throws IOException {
77
78 // Loop through the free Logical rowid list until we find
79 // the first rowid.
80 Location retval = null;
81 PageCursor curs = new PageCursor(pageman, Magic.FREELOGIDS_PAGE);
82 while (curs.next() != 0) {
83 FreeLogicalRowIdPage fp = FreeLogicalRowIdPage
84 .getFreeLogicalRowIdPageView(file.get(curs.getCurrent()));
85 int slot = fp.getFirstAllocated();
86 if (slot != -1) {
87 // got one!
88 retval =
89 new Location(fp.get(slot));
90 fp.free(slot);
91 if (fp.getCount() == 0) {
92 // page became empty - free it
93 file.release(curs.getCurrent(), false);
94 pageman.free(Magic.FREELOGIDS_PAGE, curs.getCurrent());
95 }
96 else
97 file.release(curs.getCurrent(), true);
98
99 return retval;
100 }
101 else {
102 // no luck, go to next page
103 file.release(curs.getCurrent(), false);
104 }
105 }
106 return null;
107 }
108
109 /**
110 * Puts the indicated rowid on the free list
111 */
112 void put(Location rowid)
113 throws IOException {
114
115 PhysicalRowId free = null;
116 PageCursor curs = new PageCursor(pageman, Magic.FREELOGIDS_PAGE);
117 long freePage = 0;
118 while (curs.next() != 0) {
119 freePage = curs.getCurrent();
120 BlockIo curBlock = file.get(freePage);
121 FreeLogicalRowIdPage fp = FreeLogicalRowIdPage
122 .getFreeLogicalRowIdPageView(curBlock);
123 int slot = fp.getFirstFree();
124 if (slot != -1) {
125 free = fp.alloc(slot);
126 break;
127 }
128
129 file.release(curBlock);
130 }
131 if (free == null) {
132 // No more space on the free list, add a page.
133 freePage = pageman.allocate(Magic.FREELOGIDS_PAGE);
134 BlockIo curBlock = file.get(freePage);
135 FreeLogicalRowIdPage fp =
136 FreeLogicalRowIdPage.getFreeLogicalRowIdPageView(curBlock);
137 free = fp.alloc(0);
138 }
139 free.setBlock(rowid.getBlock());
140 free.setOffset(rowid.getOffset());
141 file.release(freePage, true);
142 }
143 }